This invention relates to heating systems and more particularly to heating systems utilizing outside air.
In almost every building there is provided a heating system which utilizes a furnace having a combustion chamber. Regardless of whether it be a gas heater, an oil heater, or other types, the combustion chamber requires air to support burning of the fuel and exhaust gases are produced as a by-product of the combustion. The exhaust gases are generally emitted through a flue pipe which passes to the chimney and is thereby discharged from the building. The air for supporting combustion is generally provided by means of an air intake, usually built into the furnace. The air intake consists of an opening in the furnace wall having a grill or other air pervious cover through which the air around the furnace can pass into the furnace and to the combustion chamber.
A draft opening is usually located in the flue pipe, and a damper is frequently placed at the entrance of the opening. The draft is essential for the proper operation of the flue pipe to emit the flue gases to the chimney. One of the reasons for the draft opening is to insure an upward flow of the flue gases and prevent a reversal which would cause a backdraft into the furnace and might extinguish the fire. Another reason for such draft opening is that it permits a considerable quantity of air to be drawn from the inside of the building into the flue pipe along with the flue gases, thereby eliminating to a large extent condensation of water from the flue gases within the chimney. A further reason for the use of the draft opening is that it largely eliminates the effect of the chimney upon the furnace.
Furnaces are ordinarily constructed to have a pressure drop so that there will be a reduced pressure in the furnace to suck in a supply of air needed for support of combustion. The flow of the air through the draft opening insures that there will be no negative pressure at the furnace exhaust outlet. Were this not so, it would be difficult to balance the furnace to its own chimney condition so that the proper flow rate of air into the furnace would occur.
Therefore, the flow of air through the draft opening and into the flue pipe is of major importance in the proper operation of the furnace. Additionally, the flow of air directly into the furnace to support combustion is also of major importance. Without this air supply, improper combustion would take place and in many cases the fire might be completely extinguished.
In general, it has been the practice to vent the draft opening of the flue pipe directly to the air in the room in which the furnace is contained. Similarly, the air intake connects the furnace directly with the ambient air in the room in which the furnace is situated. As a result, the air in the immediate vicinity of the furnace is actually utilized for both air intake as well as for draft purposes.
In most cases, a furnace is situated directly within the building itself. Sometimes it is contained in its own private supply area, but frequently, it is in the basement or in a general working area of the building. Since the air around the furnace is sucked in through the flue pipe, the heated air within the room is actually being wasted since it will be exhausted out of the chimney. Such waste of heated air is most inefficient. Furthermore, since the air surrounding the furnace is sucked into the furnace to support combustion, there is a constant reduction in the amount of air in the area surrounding the furnace. As a result, fresh air must be drawn into the furnace room to resupply the void left by the air flowing into the furnace and out through the flue pipe.
When the area around the furnace is open and unrestricted, there is caused a constant drain on the heated air supply which is needed to replace the air used up by the furnace. This reduces the amount of heated air in the surrounding area and causes the furnace to operate excessively. Should the area around the furnace be enclosed in a separate room, it causes air to flow into the room through cracks and creaks in doors, windows and the like, which causes a drafty condition, as well as making the walls of the room cold, exposing any water pipes to the possibility of cold damage, and other detrimental effects.